Enzymes

Question 1

define biological catalyst

Answer 1

a molecule produced by cells (living organisms) which increases the rate of biological reactions without being changed or used during the reaction

Question 2

define activation energy

Answer 2

energy which is needed for a reaction to take place by causing bonds to break or form.
minimum amount of energy needed for a reaction to take place

Question 3

define active site

Answer 3

region where the substrate binds which has a complementary shape to the substrate where a reaction takes place

Question 4

define lock and key theory

Answer 4

shape of the enzyme fits the substrate exactly

Question 5

define the induced fit theory

Answer 5

the enzyme changes shape slightly when the substrate binds
active site is more flexible

Question 6

define enzyme

Answer 6

a globular protein that is a biological catalyst
increases the rate of reaction by lowering the activation energy needed to start the reaction

Question 7

features of the active site

Answer 7

will loose its structure if the enzyme becomes denatured
where the reaction takes place
complementary to a substrate

Question 8

stages of a reaction (enzyme and substrate)

Answer 8

substrate fits into enzyme active site
active site shape fits substrates shape
enzyme substrate complex forms
activation energy is lowered for reaction
substrate held in correct position for bonds to be broken or formed and a product is made
products are released from active site
enzyme is unchanged + ready to accept another substrate

Question 9

structure of an enzyme

Answer 9

tertiary structure
held together by hydrogen, ionic or disulphide bonds between R groups
spherical shape
hydrophilic R groups on the outside
hydrophobic R groups on the inside
polar
has an active site

Question 10

what is an intracellular enzyme

Answer 10

enzymes that catalyse reactions on the inside of the cell

Question 11

what is an extracellular enzyme

Answer 11

enzymes that catalyse reactions on the outside of the cell

Question 12

why can an enzyme only catalyse one reaction

Answer 12

active site on enzyme is only specific to one substrate
means enzyme can only catalyse reaction with complementary substrate so E-S complexes can be formed
has a specific tertiary structure

Question 13

why can a mutation in an enzyme lead to a change in the activity of an enzyme

Answer 13

alter the specific amino acid sequence
results in R groups being in different positions
hydrogen, ionic and disulphide bonds will cause protein to fold in a different secondary and tertiary structure which will code for incorrect active site
no more enzyme substrate complexes can be formed

Question 14

how do the properties of an enzyme help a reaction to happen quickly

Answer 14

biological catalysts which lower activation energy in a reaction
since this reaction happens quickly the enzyme, which will be unchanged can accept another substrate quicker

Question 15

explain the effect of increasing the enzyme concentration on the initial rate of reaction

Answer 15

as enzymes concentration increases so does the initial rate of reaction
number of enzymes increase so the number of available active sites increases
more successful frequent collisions occur
more enzyme-substrate complexes are formed
more products are created
enzyme concentration is limiting factor

Question 16

explain why the rate of reaction begins to slow down when investigating the effects of increasing enzyme concentration

Answer 16

rate becomes constant/plateaus
substrate becomes the limiting factor
not enough substrates to occupy all of the active sites on the increased amount of enzymes
more enzymes than substrates now

Question 17

explain the effect of increasing the substrate concentration on the initial rate of reaction

Answer 17

as substrate concentration increases so does the rate of reaction
more frequent successful collisions between the enzyme and substrates
more enzyme-substrate complexes formed
more products created
substrate concentration is the limiting factor

Question 18

explain why the rate of reaction begins to slow down when investigating the effects of increasing substrate concentration

Answer 18

rate becomes constant/plateaus
enzyme becomes the limiting factor
not enough enzymes to occupy all of the substrates
more substrates than enzymes now

Question 19

explain the effect of an increasing temperature on the rate of reaction

Answer 19

kinetic energy increases in both the enzyme and substrate
more successful frequent collision occur between the enzymes and substrates
more enzyme-substrate complexes are formed

Question 20

what is the effect of low temperatures on the rate of enzyme activity

Answer 20

enzymes are inactive at low temperatures
have low kinetic energy
fewer collisions between the enzymes and substrates
fewer enzyme-substrate complexes formed
rate of reaction is slow

Question 21

what is the effect of high temperatures on the rate of enzyme activity

Answer 21

enzymes denature at high temperatures
rate of reaction decreases
active site changes shape
substrate no longer fits into active site
enzyme-substrate complexes cannot be formed
products are not made